Telescoping type circuit breaker having isolator contact with arc snuffing means



July 5, 1966 R. L. RUEFFER 3,259,726

TELESCOPING TYPE CIRCUIT BREAKER HAVING ISOLATOR CONTACT WITH ARCSNUFFING MEANS Filed March 2, 1964 5 Sheets-Sheet 1 INVENTOR. RAYMOND L.RUEF'FER BY r ATTORNEY July 5, 1966 R. L. RUEFFER 3,259,726

TELESCOPING TYPE CIRCUIT BREAKER HAVING ISOLATOR CONTACT WITH ARCSNUFFING MEANS Filed March 2, 1964 5 Sheets-Sheet 5 all!!! same.

F G 6' 357 379 INVENTOR.

RAYMOND L. RUEFFER United States Patent 3,259,726 TELESCOPING TYPECIRCUIT BREAKER HAVING ISOLATOR CONTACT WITH ARC SNUFFING MEANS RaymondL. Ruelfer, Alfton, Mo., assignor to Kearney- National Inc., St. Louis,Mo., a corporation of Delaware Filed Mar. 2, 1964, Ser. No. 348,749 6Claims. (Cl. 200-151) This invention relates to a telescoping type ofdisconnect unit for an electric circuit isolator such as shown in myprior United States application for patent, Serial No. 318,637, filedOctober 24, 1963, and entitled Electric Circuit isolator. The disconnectunit constructed in accordance with the teachings of this disclosure maybe substituted for the units 140, 141 and 142 shown in my priorapplication for patent.

As explained in this prior application, an electric circuit isolator isa disconnect often used for installations, such as public buildings orother commercial users of large amounts of electric power. Theseinstallations usually carry a heavy current which may be one or morehundreds of amps at anywhere from several hundred to several thousandvolts.

A circuit isolator must effectively isolate a service circuit for safetyreasons and, in using my prior machine, it is preferable to disconnectall of the power from, or to, a service circuit before opening thecircuit isolator which, when open, isolates this particular servicecircuit to which it is connected even tho-ugh other service circuits maybe re-energized.

With the substitution of my improved units disclosed herein, it isunnecessary to disconnect the power supply before opening the isolatorbecause these improved units include arc suppressing devices so that theisolator may be opened under load in perfect safety and without the riskof damage due to arcing.

Accordingly, it is one of the objects of this invention to provide animproved disconnect unit of the telescoping type which has the addedadvantage of safe operation under heavy electric load.

It is still another object of the invention to provide an improveddisconnect unit of the telescoping type which has self-aligning contactstructure including the added advantage of safe operation by eliminatingarcing danger.

This improved unit has separable contacts to open an electric circuitand an insulator housing in which the contacts are totally enclosed whenconnected. The insulator housing opens when the contacts open so as toindicate the open relation of the contacts visually. The housing, whenopen, still conceals the contacts making them inaccessible to touch.

One of these contacts includes an arc suppressing device operatedsequentially on opening to suppress any are which might be struck due tocontact separation. The incorporation in the device of the arcsuppressor in no way changes or detracts from the self-aligning featuresbuilt into the unit as described in detail in my prior patentapplication or eliminates other features contributing to reliability andsimplicity in its operation or design.

Other objects and advantages of this invention will appear from thefollowing detailed description which is in such clear, concise and exactterms, as will enable any person skilled in the art to make and use thesame when taken in conjunction with the accompanying drawings, forming apart thereof, and in which:

FIG. 1 is an environmental view illustrating a circuit isolatorconstructed in accordance with this invention;

FIG. 2 is a perspective view with parts broken away 3,259,726 PatentedJuly 5, 1966 "ice and in section illustrating an embodiment of one unitof this invention such as shown in FIG. 1;

FIG. 3 is a fragmentary sectional view of the upper contact and aresuppressor shown in FIG. 2;

FIG. 4 is a perspective view with parts broken away and in sectionillustrating another embodiment of this invention such as used in FIG.1;

FIG. 5 is a fragmentary sectional view of the upper contact and loadinterrupter shown in FIG. 4; and

FIG. 6 is a side view of the internal mechanism within an arc suppressorshowing a modified form of brush.

One mechanism in which a unit, or units, constructed in accordance withthis invention may be mounted for operation is depicted in FIG. 1, whichmechanism is described in detail in my prior patent application hereinidentified. This description will be restricted to only so much of thisprior structure as required for an understanding of the improvement inthe unit itself.

The open box-like frame 1, shown in FIG. 1, is closed at its oppositeends 2 and 3 and at its top 4 and bottom 5. Mounting bracket 6 providesfor attachment of frame 1 to a support. The inner sides of ends 2 and 3carry vertical guide-s 9 and 11, respectively. A subframe 13 within thebox-like frame 1 has protruding guide pins 14 and 16 in the guides 9 and11 so that subframe 13 is confined to vertical movement between theclosed sides 4 and 5. Handle 18 rocks a crank shaft 19 and cranks 20 and21. Links 22 and 23 connect between the cranks and pins 14 and 16 andraise and lower the subframe 13 as handle 18 moves.

There are three units, such as ABC, in the illustrated mechanism. Eachunit is the same and all have fixed insulated parts, such as 24 and 25,received in aligned holes in the top and bottom walls 4 and 5, whichparts are held therein by screws 27 in apertured flanges 28 and screws29 in apertured flanges 30. All of these units AB-C have intermediatemovable insulator sections 32 straddled by spaced side members in subframe 13- and attached to the subframe by screws in flanges on themovable sections 32. The parts 24, 25 and 32 are hollow insulators andthe intermediate sections 32 telescope with fixed parts 24 and 25 aswill be later described. Projecting through the fixed parts 24 and 25are threaded electric terminals 33 and 34, respectively. Power feedersare connected to one set of terminals, such as 34, and a service circuitis connected to the other set of terminals 33. Operation of handle 18upwardly to the position shown in FIG. 1 connects the service circuit topower. When the handle 18 is moved downward to its lowest position, theunits open the connection between the feeders and the service circuit toisolate the service circuit from its power supply.

The description so far has been limited to the mechanism described in my.prior application for patent above identified. This invention isprimarily concerned with the construction for the units ABC which aredescribed hereinafter in detail.

FIG. 2 illustrates a construction for a unit, such as ABC shown inFIG. 1. One of the fixed parts 25 is a cup-shaped insulator surroundedby a flange, such as 30, for supporting the cup-shaped insulator 25within an aperture in the side 5 of the box-like structure 1. The closedend of the cup-shaped insulator 25 is apertured and this aperture hassecured therein the terminal 34 which projects from the outside of theinsulator and has formed thereon an electrode 36 projecting axially ofof the cup-shaped insulator 25. Slidable on the electrode 36 is tubularcontact 38. On the lower internal wall of the sleeve contact 38 is anannular head 39 slidably gripping the external surface of the electrode36. The lower end of the sleeve contact 38 is split to provide aplurality of spring fingers which are held in engagement with theelectrode 36 by a surrounding garter spring 40.

Intermediate telescoping section 32 is surrounded by an external flange42 forming the support for the intermediate telescoping sleeve 32 in thesubfraime 13. As heretofore pointed out, the flange 42 may be secured tothe s-ubfrarne 13 by screws, or clamps, so as to move with the subfra mefrom the open position of the isolator parts as depicted in FIG. 2.Internally of the telescoping intermediate insulator part 32 is asupporting flange 43. Contact sleeve 38 projects through the flange 43and is loosely received therein. A spring ring 45 seated in a groovesurrounding the contact sleeve 38 loosely abuts the lower side of theflange 43. The upper side of the flange 43 projects beneath head 46 of aplug part 47 brazed or otherwise suitably secured in the upper end ofthe sleeve contact 38. Integral with the head 46 is a blade type ofelectrode 49 provided with a spear end 50. The blade type contacts 51and 52, shown on opposite sides of the electrode 49, have a bightportion 54 slotted at 55 for the electrode 49. The bight portion 54 isbrazed or otherwise suitably secured to the head 46.

The intermediate telescoping sleeve insulator 32 has an upwardlyprojecting skirt part 57 concealing the electrode 49 and the bladecontacts 51 and 52. The skirt 57 also has an external size so as totelescope within the cup-shaped fixed part 24 on closing of the contactswithin the isolator unit. When the contacts are open, this is visiblyindicated by separation of the skirt 57 from the cup-shaped part 2.4.Protruding downwardly from the flange 42 is a lower skirt 59 which isdimensioned to telescope within the cup-shaped part 25.

The upper insulator part 24 is inverted cup-shaped and surrounded by aflange 28 by which it is supported in an aperture in top wall 4. Theclosed end of the cup 24 is aperturcd to receive the terminal 33. Thisteraninal 33 is hollow as will be pointed out hereinafter and containsan arc suppressing device 60 which includes a socket 61 of insulatingmaterial into which electrode 49 moves when the isolator unit is closed.Externally of the insulator socket 61 are a pair of flat fixed contactssuch as 62 with diagonal ribs 63 (one of which is shown in FIG. 2).Blades 51 and 52 move into face to face contact with the ribs 63 to formthe electric load carrying circuit when the isolator is closed. The aresuppressing device 60 has apertured flanges which mate with similarapertured flanges at the lower end of the terminal 33 where it projectswithin the cup-shaped insulator 24. Bolts, such as 65, secure theflanges together and the arc suppressing device within the terminal 33.Terminal 33 is externally threaded and clamped in place within the cup24 by nuts, such as 66 and 67, all as shown in FIG. 3.

Turning now to FIG. 3, the [metal ferrule part 62 of the arc breakdevice which carries the flanges and contact surfaces 63 has a rabbetedportion 95 holding a tubular extension 96. The tubular extension 96 isof metal and is stepped externally at 97 to fonm a reduced tubulardiameter extension 98. Metal casing 100 which surrounds the tubularextension 96 has a press fit in the rabbeted portion 95 and has a cap102 closing its upper end. An O-ring of rubber-like material 104 forms acushion support on the cap 102 for a disk 105. Anchored in the the diskis a plunger 106 formed of a plurality of flat strips of copper orconductor material, all of which are secured together intermediate theirends by a rivet 107. Two of the strips forming the plunger 106 andindicated as 108 and 109 form a socket-like contact electricallyconnected with plunger 106. A pair of spring pressed brushes 110 bearagainst opposite edges of the flat plunger 106 and also against thecylindrical casing 96 so as to form an electrical connection between theplunger and the metal casing. The screw 111 supports a pair of springfingers 116 and 117 which are anchored at their lower ends in oppositesnulfer elements 120 and 121. A coil spring 123 is compressed betweenthe shoulder 97 and disk and tends to hold the contacts 108 and 109 inthe position shown in FIG. 3.

The flat electrode 49 passes between the snulfer elements 120 and 121 asthe contacts are closed in the isolator. The spear end 50 protrudesbeyond the snuffer element into the arc suppressor 60 and is grippedbetween the contacts 108 and 109 of the socket type contact therein.This forms an electric connection between the electrode 49, sockets 108,109, plunger 106, brushes and metal sleeve 95 to the ferrule 62. Theferrule in turn is an integral part of the flange connection secured bythe bolts 65 to terminal 33. Contact ribs 63 also on the ferrule 62 areelectrically connected to the terminal 33.

If the contacts of the unit are opened as shown in FIG. 2 and handle 18is moved to the closed position, the intermediate section 32 movesupwardly from the position shown in FIG. 2 along with the subfrarne 13.Sleeve 32 carries tubular contact 38 and blade contacts 51, 52 as wellas electrode 49. Electric contact is maintained between the sleeve typecontact 38 and the electrode 36 as the intermediate section 32 movesupwardly. As the handle 18 continues to move, blades 51'and 52 make contact with the ribs 63 thereby completing the circuit through theisolator. Still further movement of the handle 18 forces the spear end50 into the socket formed by the contacts 108 and 109, thus, at the sametime, completing a circuit through the arc suppressing device. Bladecontacts 51 and 52 and sleeve con-tact 38 with the electrode 36 form theload carrying electric connection from terminal 33 to terminal 34, afterthe handle has moved to its full up position.

To isolate the service circuit, handle 18 is moved downwardly. Initialdownward movement of the handle separates blade contacts 51 and 52 fromthe ribs 63 so that the load is now carried to the terminal 33 throughthe flat electrode 49 and its connection between electric contacts 108and 109. As the movement of the handle 18 continues downwardly, the gripof the contacts 108 and 109 on the spear end 50 is maintained so as todraw plunger 106 downwardly compressing the spring 123. This downwardmovement not only moves the contacts 108 and 109, but also carries alongwith it the snutfers and 121 until the washer, or disk, 105 contacts theend of sleeve 96. At this point, the snutfers have been withdrawn fromthe arc suppressor as they follow the electrode 49. Contacts 108 and 109release their grip on the spear end 50 after they have reached theirlimit of downward travel. On release, spring 123 expands retracting thecontacts and the snuffers from the electrode 49. The circuit is brokenthrough the unit from the terminal 33 to the terminal 34 and at the sametime the snulfers retract within the arc suppressor coming together asshown in FIG. 3. Any are which has formed between the end of theelectrode 50 and the contacts 108 and 109 is immediately extinguished bythe snuffers whichform a barrier to arc travel between the contacts 108and 109 and the end of electrode 49. The

snuifers may be made of a resin material which will give added.

With reference to FIG. 4, the cup-shaped insulator of a fixed part 230is apertured at its closed end and, the

threaded end of terminal 234 is secured in this aperture by suitablenuts. The terminal 234 has an electrode part 236 which projects axiallywithin the cup-shaped insulator 230. Flange 229 around the cup-shapedinsulator 230 forms the means to support the fixed part 230 in anopening in the bottom wall 5 of the frame 1.

The movable insulator part 232 has one end in telescoping relation withrespect to the cup-shaped insulator part 230 and its opposite endconstructed and arranged to telescope within the cup-shaped insulatorpart 224. Flange 242 around the insulator is a support for the movableinsulator part 232 in the subfra-me 13. Internal shoulder 243 oninsulator 232 is arranged to support the external annular flange 246 onthe metal bushing 247. There is an annular depending skirt 253 on thebushing 247. A contact sleeve 238 is secured on the skirt 253 by brazingand telescopes with the electrode 236. Contact is made through anannular rib 239 within the contact sleeve 238 and the end of this sleeveis split to form spring fingers, all as described in my prior patentapplication above identified. Garter spring 240 is seated in an annulargroove around the sleeve contact 238.

The bushing 247 is centrally apertured for slidably holding an electroderod 254. A spring 255 surrounds the rod 254 and is compressed between aseat on the skirt 253 and a washer 256 held on the threaded end of therod 254. The upper end of the rod 254 is slotted and the slot receivesthe end of a flat blade type electrode 249 securely anchored to the rod254 within the slot. Since the blade 249 is wider than the diameter ofthe rod 254, it has protruding edges which act as stops to preventfurther expansion of spring 255. The edges contact the upper surface ofthe bushing 247. Brushes 259 on the bushing 247 form an electricconnection to the rod 254 and from the rod 254 to blade 249. A sleevecontact 252 is brazed to the bushing 247 and surrounds electrode blade249. The internal annular rib 251 forms the electric contact surfacewhen telescoped with the tubular contact 262 which is a stationaryelectrode and part of an assembly including terminal 233 in cup 224. Theend of the tubular contact 252 may be slotted to form spring fingers asdescribed in my prior application. Garter spring 293 is seated in thegroove around the end of contact sleeve 252.

The flange 246 is suitably secured by pins 241 to internal shoulder 243so that both sleeve contacts 238 and 252 move with movable insulatorpart 232. Pins 241, above-mentioned, may be received in slots within theflange 246 to provide for some floating movement of the bushing 247 withrespect to the supporting shoulder 243. Flexibility of this kind is adistinct benefit during engagement of the contacts of the isolator.Regardless of how the flange 246 is secured on the shoulder 243, blade249 is positively moved by the shoulder with the intermediate movableinsulator part 232 in a direction to telescope within contact 262. Onreverse movement of the insulator part 232, spring 255 is a yieldingconnection for moving the electrode 249. As will be pointed outhereinafter, the spring 255 is so selected that movement of theelectrode 249 is not compelled until the spring 255 is compressed solid.This is due to the fact that the spear end 250 has a tendency to hang inthe are suppressor device 260 as hereinafter described.

Sleeve contacts 238 and 252 are electrically connected through bushing247 and both are electrically connected with electrode 249 throughbrushes 259. When the sleeve contact 252 is telescoped with electrode262 an electric circuit is completed from terminal 233 to terminal 234through electrode 262, sleeve 252, bushing 247, sl'eeve contact 238 toelectrode 236 and terminal 234.

Details of the second circuit from the blade electrode 249 through thearc suppressor 260 are more clearly shown in FIG. 5. Turning now to FIG.5, it will be observed that terminal 233 has a threaded socket 270 aswell as an externally threaded end. Arc suppressor 260 has a tubularcasing 272 externally threaded to mate with threads 271 on the inside ofsocket 270. Nut 273 internally of the insulator cup 224 forms a rigidconnection mounting the terminal 233 and the arc suppressing device 260in the end of the insulator cup 224.

Internal threads 274 in the end of the casing of the are suppressor 260form a connection with external threads 275 on the end of electrode 262.There is a reduced tubular extension 276 on electrode 262 and aninternal shoulder 277 at the junction between the part with threads 275,and the extension thereon 276.

Electrode 262 is electrically connected with a metal plunger 280 bybrushes 279 which have a free end biased against one side of plunger 280and the opposite end clamped between shoulder 277 and an end of aninsulated tubular guide 282 which projects from within electrode 262.Plunger 280 is in turn electrically and mechanically connected withsocket members 285 which are spring fingers gripping the spear end 250,or blade electrode 249. A pair of leaf springs 287 are secured at oneend to opposite sides of the plunger 280 by connector 289 and carry apair of snufi'ers 290 on their free ends. The snuflers are pressedagainst opposite sides of blades 249.

The plunger 280 has one end anchored in a disk 292 which is held againstO-ring 294 forming a cushion between disk 292 and a plug 295 closing thecasing 272. A spring 296 is compressed between the disk 292 and thethreaded part 275 of electrode 262.

When the isolator unit is closed, the electric circuit is completed notonly between the contacts 252 and 238 with electrodes 262 and 236 asdescribed, but also through the arc suppressor 260 from blade 249 tosocket 285, plunger 280, brushes 279, casing 272 and terminal 233.During the opening operation of the unit, movable insulator 232 travelsin a direction from within cup insulator 224. The sleeve contact 252separates from electrode 262, but there will be no arc since a parallelcircuit through the arc suppressor from blade 249 to socket 285 is stilloperative. As the movement of movable insulator 232 continues, spring255 is compressed because the spear end 250, or blade 249, isfrictionally held in the socket 285. After a predetermined separation,but preferably while the end of insualtor 232 is still within the cupinsulator 224, spring 2255 becomes solid and, thereafter, continuedmovement draws socket 285 and snuffers 290 toward the end of tube 282,compressing spring 296. When disk 292 contacts the end of extension 276,blade 249 is freed from socket 285. Spring 289 expands retracting socket285 and withdrawing snuifers 290 which come together as they move intotube 282 and form a bar rier to arc travel from the socket 285 toelectrode 249. Both snuifers 290 and tube 282 may be formed of a resinwhich gives off a gas when an arc is formed. At the same time thatspring 296 is retracting socket 285, spring 296expands withdrawing theblade 249 away from the arc suppressor 269. These events all take placeafter the end of movable insulator 232 has withdrawn from cup 224 sothat the action is observable to the operator. When the handle 18reaches the end of its travel, electrode 249 has withdrawn into movableinsulator 232.

Turning now to FIG. 6, therein shown is a sub-assembly of parts for anarc suppressor such as heretofore described and as shown specifically inFIG. 5. Corresponding parts in FIG. 6 are indicated by the samereference characters used in FIG. 5 with added.

As in FIG. 5, the snutfers 390 are mounted on leaf springs 387 andfastened to the plunger 380 by connector 389. The electric socket, orgripper contact, 385 is formed at one end of the plunger 380' and theopposite end of the plunger is notched to hold a disk, such as 292 shownin FIG. 5 on the end of the plunger 280. As also shown in FIG. 5, theplunger 380 of FIG. 6 comprises two strips Of metal side by side heldtogether by rivets A and B. In this modification, the electricconnection is made between the plunger 380 and the casing 372 by a brushin the form of a wire bail 379 frictionally clamped between the stripsof the plunger 380 at points on opposite sides of the rivets A and B.The ends of the bail 379 are left open to permit expansion and traction.

Each leg of the bail 379 makes sliding contact with the inner surface ofthe casing 372 on the outside of the spring 396 so as to electricallyconnect the plunger 380 and the socket 385 with the casing 372. Thebrush 379 can be made of a suitable metal which is springy, such asPhosphorbronze. As will be apparent from a comparison of FIGS. and 6,the bail 379 is a full-floating electric brush and replaces the pair offixed brushes 279 in FIG. 5.

Changes in and modifications of the structure described may be madeWithout departing from the spirit of my invention or sacrificing itsadvantages.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. In an electric circuit isolator having a first fixed contact member;a second fixed contact member;

means mounting said contact members in substantial alignment and spaceda substantial distance apart; and a bridging member mounted forrectilinear movement between said contact members to make and break acircuit therebetween, said bridging member being continuouslyelectrically connected to said first fixed contact member but movablerelative thereto, and being selectively electrically connected to anddisconnected from said second fixed contact member, the improvementwhich comprises: said bridging member having:

(a) a main contact selectively engageable with said second fixed contactmember,

(b) a spear contact permanently electrically and mechanically connectedto said main contact and continuously electrically connected with saidfirst fixed contact member,

said second fixed contact member having electrically connected thereto,a gripper contact member, said gripper contact member:

(c) being spring mounted for limited rectilinear movement toward andaway from said first fixed contact member,

(d) being constantly spring biased in a direction away from said firstfixed contact member,

(e) having means for receiving and resiliently gripping said spearcontact when said main contact and said second fixed contact areengaged; and

(f) having an arc snuffer mounted thereon, movable therewith andprojecting therefrom for a substantial distance toward said first fixedcontact, said are snuffer providing a channel for traverse by said spearcontact to and from said means (e),

the gripping force exerted by said means (e) upon said spear contactbeing so coordinated with the spring bias on said gripper contact memberthat during circuit interruption the gripper contact member moves withsaid spear contact until said main contact has separated from saidsecond fixed contact.

2. The improvement of claim 1 wherein the gripper contact member isdisposed within an electrically conductive tube electrically andmechanically connected with said second fixed contact member, the axisof said tube being parallel with said rectilinear movement, and aspring-biased brush for maintaining said gripper contact member inelectrical connection with said tube. 3. The improvement of claim 2wherein the springbiased brush is a hair-pin spring movable with saidgripper contact member, the legs of said hair-pin spring beingbiasedinto electrical contact with the interior of said tube atsubstantially diametrically opposite points.

4. The improvement of claim 1 wherein said arc snuffer is composed of aplurality of elementstormed of gasemitting material, and said elementsare connected to said gripper contact member, by spring'fingers.

5. The improvement of claim 1 wherein said gripper contact member ismounted upon a plunger disposed within a tubular casing fixed relativeto said second fixed contact and whose axis is substantially parallelwith said rectilinear movement, said plunger being anchored to diskwhose outside diameter corresponds substantially with the insidediameter of said tubular casing, said disk being free to move axially ofsaid tubular casing and being References Cited by the Examiner UNITEDSTATES PATENTS 2,267,399 12/1941 Farrer et'al. 200-146 X 2,841,6727/1958 Hoye 200l63' 3,060,285 10/1962 Steinbruner 20077 X ROBERT K.SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, Examiner.

P. E. CRAWFORD, Assistant Examiner.

1. IN AN ELECTRIC CIRCUIT ISOLATOR HAVING A FIRST FIXED CONTACT MEMBER;A SECOND FIXED CONTACT MEMBER; MEANS MOUNTING SAID CONTACT MEMBERS INSUBSTANTIAL ALIGNMENT AND SPACED A SUBSTANTIAL DISTANCE APART; AND ABRIDGING MEMBER MOUNTED FOR RECTILINEAR MOVEMENT BETWEEN SAID CONTACTMEMBERS TO MAKE AND BREAK A CIRCUIT THEREBETWEEN, SAID BRIDGING MEMBERBEING CONTINUOUSLY ELECTRICALLY CONNECTED TO SAID FIRST FIXED CONTACTMEMBER BUT MOVABLE RELATIVE THERETO, AND BEING SELECTIVELY ELECTRICALLYCONNECTED TO AND DISCONNECTED FROM SAID SECOND FIXED CONTACT MEMBER, THEIMPROVEMENT WITH COMPRISES: SAID BRIDGING MEMBER HAVING: (A) A MAINCONTACT SELECTIVELY ENGAGEABLE WITH SAID SECOND FIXED CONTACT MEMBER,(B) A SPEAR CONTACT PERMANENTLY ELECTRICALLY AND MECHANICALLY CONNECTEDTO SAID MAIN CONTACT AND CONTINUOUSLY ELECTRICALLY CONNECTED WITH SAIDFIRST FIXED CONTACT MEMBER, SAID SECOND FIXED CONTACT MEMBER HAVINGELECTRICALLY CONNECTED THERETO, A GRIPPER CONTACT MEMBER, SAID GRIPPERCONTACT MEMBER: (C) BEING SPRING MOUNTED FOR LIMITED RECTILINEARMOVEMENT TOWARD AND AWAY FROM SAID FIRST FIXED CONTACT MEMBER, (D) BEINGCONSTANTLY SPRING BIASED IN A DIRECTION AWAY FROM SAID FIRST FIXEDCONTACT MEMBER, (E) HAVING MEANS FOR RECEIVING AND RESILIENTLY GRIPPINGSAID SPEAR CONTACT WHEN SAID MAIN CONTACT AND SAID SECOND FIXED CONTACTARE ENGAGED; AND (F) HAVING AN ARC SNUFFER MOUNTED THEREON, MOVABLETHEREWITH AND PROJECTING THEREFROM FOR A SUBSTANTIAL DISTANCE FORWARDSAID FIRST FIXED CONTACT, SAID ARC SNUFFER PROVIDING A CHANNEL FORTRAVERSE BY SAID SPEAR CONTACT TO AND FROM SAID MEANS (E), THE GRIPPINGFORCE EXERTED BY SAID MEANS (E) UPON SAID SPEAR CONTACT BEING SOCOORDINATED WITH THE SPRING BIAS ON SAID GRIPPER CONTACT MEMBER THATDURING CIRCUIT INTERRUPTION THE GRIPPER CONTACT MEMBER MOVES WITH SAIDSPEAR CONTACT UNTIL SAID MAIN CONTACT HAS SEPARATED FROM SAID SECONDFIXED CONTACT.